The Dow Jones industrial average plunged 420 points Thursday following an announcement by President Donald Trump that he would place new taxes on imported steel and aluminum. The index was down 589 points at its worst levels of the day.

The S&P 500 closed down 1.32%, making for the first time January 2016 that it fell more than 1% in three consecutive sessions. The Nasdaq 100 finished down 1.51%.

"Our Steel and Aluminum industries (and many others) have been decimated by decades of unfair trade and bad policy with countries from around the world,” Trump tweeted Thursday morning. “We must not let our country, companies and workers be taken advantage of any longer. We want free, fair and SMART TRADE!"'

Speaking on CNBC, Dan DiMicco, former CEO of steel producer Nucor, said a $1,000-per-ton increase in the price of steel could raise the price of a car by $200 or more. Shares of the company gained 3%.

Stocks slide

Markets tanked as investors digested what the new taxes might mean for the economy — and the tariffs could have devastating consequences. Economists worry that increased trade protections on steel and aluminum could cause the downstream prices of goods that use those products to increase, leading to inflationary pressures in the US economy.

Among those already feeling the pain were beer producers, who responded to the Commerce Department's recommendations with a warning that an aluminum tariff could drive up the cost of beer cans and then what customers pay.